1. Technical Field
This application is related to electrical contacts or electrodes for large area electro-optic devices, and more specifically, for electrical contacts for modulating retroreflectors, photodiodes, and other large area optoelectronic devices.
2. Related Technologies
Large area surface-normal optoelectronic devices include modulating retroreflectors (MRR) and large area photodiodes (PDs). Both MRRs and PDs can be designed either with or without focusing optics.
A modulating retroreflector developed by the Naval Research Laboratory is described in U.S. Pat. No. 6,154,299 to G. Charmaine Gilbreath, Steven R. Bowman, William S. Rabinovich, Charles H. Merk, and H. E. Senasack, “Modulating retroreflector using multiple quantum well technology”, the entire disclosure of which is incorporated by reference herein. The modulating retroreflector allows free-space optical communication between a node with minimal power, weight, and pointing ability (e.g., a UAV) and a node with higher power, weight, and pointing ability (e.g. a ground station).
Modulating retroreflectors were demonstrated before the invention of the laser, but were restricted to short distances and low data rates. The first known description of a modulating retroreflector for free-space optical communication is in Harry Stockman, “Communications by Means of Reflected Power,” Proceedings of the IRE, pp. 1196-1204, October 1948. Recent advances in optoelectronic devices and free-space optics have greatly increased the capabilities of MRR systems. Examples are discussed in “Peter G. Goetz, William S. Rabinovich, Rita Mahon, Mike S. Ferraro, James L. Murphy, H. Ray Burris, Mena F. Stell, Chris I. Moore, Michelle R. Suite, Wade Freeman, G. C. Gilbreath, and Steven C. Binari, “Modulating Retro-Reflector Devices and Current Link Performance at the Naval Research Laboratory,” MILCOM 2007, Orlando, Fla., October 2007.”
There are two basic classes of retro-reflectors, “cat's eye” and corner cube retro-reflectors. “Cat's eye” retro-reflectors combine lenses and/or mirrors and incorporate an optical focus. Several variations of cat's eye retro-reflectors are described in in Mark L. Biermann, et al, “Design and analysis of a diffraction-limited cat's-eye retroreflector,” Opt. Eng. 41, 1655 (2002).
Corner cube retro-reflectors (CCRs) are nonfocusing. Tradeoffs between modulating retro-reflectors of the corner cube type and the cat's eye type are discussed in “Peter G. Goetz, William S. Rabinovich, Rita Mahon, Lee Swingen, G. Charmaine Gilbreath, and James Murphy, “Practical Considerations of Retroreflector Choice in Modulating Retroreflector Systems,” IEEE LEOS 2005 Summer Topicals, talk TuA3.5, San Diego, Calif., 25-27 Jul. 2005.
Gridded electrodes for use in solar photovoltaic cells are discussed in H. B. Serreze, “Optimizing Solar Cell Performance by Simultaneous Consideration of Grid Pattern Design and Interconnect Configuration,” 1978. Conference Record of the IEEE Photovoltaic Specialists Conference pp. 609-614, 13th IEEE PVSC, pp. 609-614, 1978, and in A. R. Burgers, “How to design optimal metallization patterns for solar cells”, Progress in Photovoltaics: Research and Applications; Vol. 7, No. 6, pp 457-461, 1999.